With centrifugal pumps, it is counted as belonging to the state of the art to integrate a non-return valve within the pump, in order to prevent delivered fluid from being able to flow back through the pump. Such a non-return valve in particular is envisaged with multi-stage submersible pumps, in order to prevent a backflow through the pump, given a standstill of the pump.
The invention departs from a multi-stage submersible pump of the type Grundfos SP 30. With regard to this pump, it is the case of a well pump which in the operational position comprises a drive motor at the bottom, with a coupling arranged thereabove. The drive motor is connected via the coupling to several pump stages which are arranged thereabove and which are driven by a common shaft. A housing part connects to a last pump stage and comprises a non-return valve and just as the coupling comprises lateral recesses, into which positive fit elements engage, said elements being seated at the ends of tension/clamping straps, with which the pump stages between the end-side housing part and the coupling are clamped and mechanically connected.
The non-return valve of the end-side housing part is designed as a weld construction and is formed from sheet-metal parts. It comprises a sealing ring which is integrated into an annularly peripheral groove and which forms the contact surface for a sealing body which is likewise formed of sheet metal and is essentially plate-like. A guide in the form of guide arms and which guides the sealing body between its closure position and the releasing opened position is formed within the valve.
Although the pump is basically conceived for the uprightly standing operation, it can also be operated in a lying manner. In lying operation, the known non-return valve in particular can have problems with regard to the sealedness, if the valve plate comes to bear on the sealing seat in a non-centered manner due to gravity.
Moreover, the non-return valve can only be exchanged as a whole, since neither the seal nor the component receiving this or the valve plate can be removed from the valve housing which is designed as a closed welded construction.